This invention relates to a process and apparatus for the continual manufacture of staple fibers from thermoplastic materials, such as fully synthetic, filament-forming high polymers, polyethyleneterephthalates, or the like, by melt spinning, drawing and cutting in one operating phase at melt spinning speeds exceeding 3,000 m/min.
In presently used processes for the manufacture of staple fibers from thermoplastic polymer filaments, two consecutive processing steps are required. In the first step, the spun filaments are joined to each other to form a cable and the cable is deposited in cans. In the succeeding second step, the cables are withdrawn from groups of cans, are joined together, after-treated, drawn, fixed, crimped, and finally cut. At the present time, spinning speeds range between 1,000 and 4,000 m/min, whereas, drawing speeds range only between 100 and 200 m/min. A combined process is economically feasible only if these spinning speeds can be substantially maintained.
In one of the processes already proposed, namely, that shown in German Offenlegungsschrift No. 2,360,854, filaments, spun at high speed, are drawn by injector nozzle means and blown into an inclined cyclone tube, so that loops are produced. These loops are pulled out of the discharge end of the cyclone tube at a speed which amounts, however, to only one-tenth to one-five-hundredth of the speed at which the filaments are supplied to the cylone tube. Thus, the loops are laid one above the other and produce a cable. This cable is then prepared, as described above, crimped and cut in a continual process.
The proposed process has the drawback that, in accordance with where the loop is cut, filament lengths are produced which in the most unfavorable case amount to the double length of a cut or, in extreme cases, only to a few millimeters. Particularly, excessively long filaments present problems for further processing.
With processes proposed in British Pat. Nos. 824,223 and 796,684, loops are also produced but by inserting rods perpendicular to the moving direction of the approaching filaments. Aside from the fact that, at very high speeds, it becomes difficult to separate the filaments from the rods, in this case also both extremely long and extremely short filaments are produced.
Bearing in mind the disadvantages of the known processes or the proposed processes, the objective of the present invention is to provide a process and apparatus, for the continual manufacture of staple fibers, which avoids both extra long and extremely short filaments.